The ETF2009 shootout was a contest of single-ended output transformers. Scroll down to see the results and pictures.
Â The test amplifier will be a 310A+300B "l'audiophile" (without negative feedback), and the speaker willÂ have high sensitivity, passive crossover, more or less 8 ohm impedance.
Â The shootout listening tests will be MONOPHONIC : there is no need to bring a pair of identical transformers, one is enough.
Â The B+ voltage is about 430VDC, and the primary will have to handle 70mA DC.
The negative tap of theÂ secondary will be joined to earth.
Â The impedance ratio can go from 2.2K / 8 ohm to 3.6K / 8 ohm.
The test amplifier has 4 female 4mm banana plug (IEC 1010 compatible) :
B+ (high voltage 430VDC) : Red
P (plate of the 300B) : Yellow
0 (earth of the amplifier, and negative input of the speaker) : Black
8 (positive input of the speaker) : White
How to register to the shootout ?
- First of all, you have to register to the triode festivalÂ : Â http://www.melaudia.net/subscribeETF.php
- Â On your registration form, fill the "participate to the shootout with" field with the name of your transformer (brand and reference, or any description if it is a DIY transformer)
- Â Bring one transformer with the cords+ 4mm banana plug at ETF
Participants are asked to :
Â Make sure that the transformer is not phase-inverting (but it is not disqualifying)
clearly identify each tap that plugs into the test amplifier (color and/or name)
provide 0.5 to 1m cords with 4mm male bananaÂ (IEC 1010 is recommanded)
Pay attention to insulation problems :
Before the shootout, the following tests will be performed :
- a 500V insulation test between B+ and 0 tap.
- turn ratio measurement.
- phase/out-of-phase check.
Special stuff :
Parafeed transformers (choke + condensator + transformer without air gap) are authorized.
DIY transformers are especially welcomed, but here again, pay attention to insulation.
mismatchs (5K to 16 ohm, used as 2.5K to 8 ohm, for instance)Â are authorized, but please indicate clearly which secondary tap you want to plug on the speakers, and which primary tap you want to use.
primary and/or secondary compensations are authorized (zobel network or whatever you want,Â providing it is not dangerous)
Sorry, negative feedbackÂ is forbidden.
Â THE SETUP
Krell CD Transport and Wadia D/A converter
The WE310A+WE300B amplifier used for the shootout. There is no output transformer, but two sets of banana female plugs: B+ (red), 300B Plate (yellow), ground (black) and 8 ohm (white). A switch connects the transformer A or B.
The mono line preamp used for the shootout. Sowter multitap transformer for the volume, Tango output transformer (500 or 600 ohm external load).
A 10 turns 500 ohm potentiometer was used to calibrate the output level of each transformer. It is also the external load of the preamplifier.
The loudspeaker used for the shootout : Great Plain AudioÂ 515 and 399, with Westrex acoustilens horn.
31 transformers ready for the shoot-out !!!
list of participants :
|29||BlÃ¶hbaum, Frank||PPÂ output transformer, with oneÂ primary winding compensating the current of the 300B.Â|
|16||Dolinskyi, Arkadii||DIY EI transformer|
|15||Hasling, Per + Ole||SE Silk transformer from Tailand 3,0 kOhm|
|1||HÃ¸jbjerg, Karsten||toroidal transformer in cardbox|
|24||Hubertse, Rob||custom made OPT by AE-Europe.|
|9||Michimori, Hirokuni||ex-Tango #10887 (special order), rating 50W, 3.5K/4,8,and16ohm,with 360hm KNFB winding|
|26||Monmagnon, Yves||Dissident audio transformer|
|14||Raudonat, Ralf||yes, with output transformer regarding the terms|
|18||Schwarz, Andreas||a selfmade single ended output transformer|
|2||Terrell, Brian||SE Output transformer|
|7||Veen, van der, Menno||Â toroidal SE-OPT's|
|11||Weidhase, Ulf||One Parafeed Transformer 3k5 /8 Ohm Transformer|
|23||Willenswaard, van, Peter||AudioNote Trans-300 double-C-core|
|19||Polisois, Aristide||DIY toroid transformer|
|13||Â||DIY grey transformer|
|5||Falampin, JÃ©rÃ´me||Unknown semi-pro vintage transformer (in tea box)|
|3||Bouyer ST10 transformer (in soap box)|
|21||parafeed transformer (9H cheap chinese choke, 1ÂµF cap, 50VA toroid power transformer 220V -> 12V) in biscuit box|
|25||Le ClÃ©ac'h, Jean-Michel||small and old Audionote classA|
|8||Magnetics (special order),Â|
|12||Â Meigxu (Mingda),|
|6||Sullerot, Julien||Partridge TK 4519|
|10||Tamura transformer from a Sun Audio 2A3 amp|
|28||Pierre-Francois Brand||Spanish transformer|
|27||Pierre-Francois Brand||R-core Softone RW-20Â : http://www.icl.co.jp/audio/english/RW20.htm|
some pictures of the transformers :
Peter van Willenswaard (right) won with an Audionote Trans-300 double-C-core, and receives a pair of TJ 300B from Julien (left).
Jean-MichelÂ measuringÂ a transformer. Measurements (distortion, bandwidh, impulse response) have been made with 70mA through the primary.
See theÂ measurements hereÂ .